Please refer to FIG. 1 and FIG. 2, which are a sectional sketch of an edge of an antenna in prior arts and a sectional sketch for stacking a plurality of antennas in prior arts. Originally the edge of the antenna is assembled by a supporting ring 110 and a base 120 holding the supporting ring 110. The antennas may be stacked flat for delivery after manufacturing. Due to the wide angle between a bottom edge 121 and a side edge 122 of the base 120 greater than 90 degrees making the condition of the slippery supporting ring 110 of a bottom antenna 100 and the supporting ring 110 of the bottom antenna 100 sustaining the base 120 of a top antenna 100 via only a point 123 while in stacking, the top antenna 100 may then be unstable to fall down as the position of an antenna 100′. Therefore to design a structure for firmly stacking antennas and preventing the conditions of damage to the antennas and occupying the space of a container shall be a very important issue.